Pigments are widely used in many industries to impart basically a pleasing, esthetic color and appearance to various media in which they are mixed, such as paints, varnishes, lacquers, organic resins, glazes, ceramic ware such as procelain enamels, glass, and the like. As a general rule, inorganic pigments have a greater scope of application as compared to organic pigments. Because of the more severe and drastic conditions of use in glazes and ceramic applications, particularly with reference to temperature of preparation, inorganic pigments must be used for such applications. However, inorganic pigments may also be added to organic media, such as organic resinous polymeric materials, especially when such materials are used at relatively high temperatures such as in extruding or molding.
Important inorganic red pigments include those of the cadmium sulfide-cadmium selenide series. Two additionally important inorganic yellow pigments are based on cadmium sulfide and lead antimonate (Naples Yellow). As awareness of the need for environmental protection grows, industrial use of toxic and semi-toxic chemicals has come under greater scrutiny and criticism. The use of such metals as cadmium, selenium, lead and antimony, previously extensively employed in preparing pigments, has accordingly become less popular. Stronger governmental regulation and control of their use are expected. It is, therefore, important to develop substitute pigments.